U.S. patent number 6,428,541 [Application Number 09/287,917] was granted by the patent office on 2002-08-06 for method and instrumentation for vertebral interbody fusion.
This patent grant is currently assigned to SDGI Holdings, Inc.. Invention is credited to Lawrence M. Boyd, Bradley T. Estes, Mingyan Liu, Eddie Ray, III.
United States Patent |
6,428,541 |
Boyd , et al. |
August 6, 2002 |
**Please see images for:
( Certificate of Correction ) ** |
Method and instrumentation for vertebral interbody fusion
Abstract
A method and instrumentation particularly adapted for disc space
preparation from an anterior approach to the spine. In one aspect,
an expandable template is provided having guides to guide a cutting
device for bilateral formation of openings in the disc space. In
another aspect, an improved guide member is provided for guiding a
cutting tool. Still further, the invention provides an improved
double barrel guide sleeve with a central distraction extension and
lateral non-distracting extensions. Optionally, the guide sleeve
includes windows and covers to selectively cover the windows. An
improved reamer with an internal chamber and optional modular
coupling is also provided. A depth stop is provided to selectively
engage a tool shaft and a guide sleeve to control tool penetration
into the disc space. A method of using the disclosed instruments is
also provided.
Inventors: |
Boyd; Lawrence M. (Memphis,
TN), Ray, III; Eddie (Cordova, TN), Estes; Bradley T.
(Memphis, TN), Liu; Mingyan (Bourge la Reine,
FR) |
Assignee: |
SDGI Holdings, Inc.
(Wilmington, DE)
|
Family
ID: |
36928798 |
Appl.
No.: |
09/287,917 |
Filed: |
April 7, 1999 |
Current U.S.
Class: |
606/86A |
Current CPC
Class: |
A61F
2/4611 (20130101); A61B 17/1757 (20130101); A61B
17/025 (20130101); A61B 17/1671 (20130101); A61B
17/1615 (20130101); A61B 2017/3445 (20130101); A61F
2002/4627 (20130101); A61B 17/1637 (20130101); A61B
2090/034 (20160201); A61F 2002/4687 (20130101); A61B
17/1655 (20130101); A61B 17/1617 (20130101); A61B
2090/062 (20160201); A61B 2017/0256 (20130101) |
Current International
Class: |
A61F
2/46 (20060101); A61B 17/02 (20060101); A61B
17/16 (20060101); A61B 17/17 (20060101); A61B
19/00 (20060101); A61B 017/56 () |
Field of
Search: |
;606/60,61,62,57,79,80,86,90,96,97,99,105 ;D24/146,144,170
;604/22,902 ;600/533,538 ;128/204.25,205.11,207.17,207.14
;623/17 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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Other References
"XP-002121982," Section PQ, Week 9524; Derwent Publications Ltd.
.
"Posterior Lumbar Interbody Fusion with Specialized Instruments,"
by Gabriel W.C. Ma, F.A.C.S., pp. 57-63. .
"The Prefit Dowel Interbertebral Body Fusion as Used in Lumbar Disc
Therapy," by B.R. Wiltberger, M.D., pp. 723-727. .
"The Dowel Intervertebral-Body Fusion as Used in Lumbar-Disc
Surgery," by B.R. Wiltberger, M.D., pp. 284-292. .
"Surgical Technique Using Bone Dowel Instrumentation--For Posterior
Approach," Sofamor Danek brochure. .
"MD-III Threaded Cortical Dowel--Design Rationale and Surgical
Technique," University of Florida Tissue Bank brochure. .
"Lumbar I/F Cage With VSP Spinal System for PLIF," by John W.
Brantigan, M.D..
|
Primary Examiner: Garbe; Stephen P.
Assistant Examiner: Ngo; Lien
Attorney, Agent or Firm: Woodard, Emhardt, Naughton,
Moriarty & McNett
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims the benefit of Provisional
Application Ser. No. 60/081,206, filed Apr. 9, 1998, the contents
of which are hereby incorporated by reference in their entirety.
Claims
We claim:
1. A guide sleeve assembly for defining a protected passageway to a
disc space, comprising: a first tube defining a first working
channel, and a first bone engaging end; a second tube defining a
second working channel and a second bone engaging end, said second
tube connected to said first tube with said second bone engaging
end disposed adjacent said first bone engaging end; a central
distracting extension disposed between said first working channel
and said second working channel adjacent said first and second bone
engaging ends, said central distracting extension having a first
height, a first lateral extension extending from said first bone
engaging end opposite said central distracting extension, said
first lateral extension having a second height; and a second
lateral extension extending from said second bone engaging end
opposite said central distracting extension, said second lateral
extension having a third height, said first height greater than
said second height and said third height, wherein said central
distracting extension maintains distraction in a disc space and
said first and second lateral extensions inhibit encroachment of
adjacent tissue into said first and second channels.
2. The guide sleeve assembly of claim 1, wherein said bone engaging
end includes spikes for engaging vertebral bodies.
3. The guide sleeve assembly of claim 1, wherein the assembly has a
proximal end opposite said bone engaging ends, said proximal end
having a first width, said first bone engaging end and said second
bone engaging end defining a second width, said first width greater
than said second width.
4. The guide sleeve assembly of claim 1, wherein said first tube
has an outer surface and said first tube defines at least one
window extending from said outer surface to said first working
channel.
5. The guide sleeve assembly of claim 4, further comprising a cover
disposed on said outer surface adjacent said window of said first
tube, wherein said cover is adapted to selectively cover said
window.
6. The guide sleeve assembly of claim 5, wherein said cover has a
cylindrical shape.
7. The guide sleeve assembly of claim 4, wherein said second tube
has at least one window defined therein.
8. The guide sleeve assembly of claim 1, wherein said first and
second tubes extend along a longitudinal axis and have a proximal
portion opposite said first and second bone engaging ends, wherein
said proximal portion of said first and second tubes has a first
width transverse to said longitudinal axis, wherein said first and
second tubes at said bone engaging ends combined have a second
width transverse to said longitudinal axis, wherein said second
width is less than said first width.
9. A guide sleeve assembly for defining a protective passageway in
a patient, comprising: a guide sleeve, said guide sleeve including
a first tube defining a first working channel, and a second tube
laterally joined to said first tube, said second tube defining a
second working channel; and wherein said guide sleeve has a
proximal portion and an opposite distal portion adapted for
insertion into the patient, said proximal portion having a first
outer width that spans said first and second tubes, said distal
portion having a second outer width that spans said first and
second tubes, wherein said second outer width is smaller than said
first outer width.
10. The guide sleeve assembly of claim 9, wherein said first and
second tubes have reduced wall thicknesses at said distal
portion.
11. The guide sleeve assembly of claim 9, wherein said first and
second tubes have circular cross sections.
12. The guide sleeve assembly of claim 9, wherein said first tube
has at least one window defined therein.
13. The guide sleeve assembly of claim 12, further comprising a
cover constructed and. arranged to selectively cover said
window.
14. The guide sleeve assembly of claim 13, wherein said cover is
slidably disposed on said first member.
15. The guide sleeve assembly of claim 13, wherein said cover has a
partial cylindrical shape.
16. The guide sleeve assembly of claim 9, wherein said second tube
has at least one window defined therein.
17. The guide sleeve assembly of claim 9, further comprising a
central distracting extension disposed between said first working
channel and said second working channel at said distal portion.
18. The guide sleeve assembly of claim 9, wherein said guide sleeve
has a barrel tip removably coupled thereto.
19. The guide sleeve assembly of claim 12, further comprising:
wherein said second tube has at least one window defined therein;
and a cover constructed and arranged to selectively cover said
windows in said first and second tubes.
20. The guide sleeve assembly of claim 12, further comprising:
wherein said second tube has at least one window defined therein; a
first cover constructed and arranged to selectively cover said
window in said first tube; and a second cover constructed and
arranged to selectively cover said window in said second tube.
21. The guide sleeve assembly of claim 20, wherein said first and
second covers each has a partial cylindrical shape.
22. A guide sleeve assembly for defining a protective passageway in
tissue of a patient, comprising: a tube defining an interior
working channel adapted to receive surgical instruments, wherein
said tube has at least one visualization window defined therein for
viewing the surgical instruments in said interior channel; a cover
disposed on said tube adjacent said window, said cover being
adapted to selectively cover said window to prevent tissue invasion
into said interior channel through said window; and wherein said
cover includes an outwardly extending flange, said flange adapted
to retract tissue disposed adjacent said tube.
23. A guide sleeve assembly for defining a protective passageway in
tissue of a patient, comprising: a tube defining an interior
working channel adapted to receive surgical instruments, wherein
said tube has at least one visualization window defined therein for
viewing the surgical instruments in said interior channel; a cover
disposed on said tube adjacent said window, said cover being
adapted to selectively cover said window to prevent tissue invasion
into said interior channel through said window; and a second tube
laterally joined to said tube, said second tube having at least one
visualization window defined therein, wherein said cover is further
adapted to selectively cover said visualization window of said
second tube.
24. The guide sleeve assembly of claim 23, wherein said cover
includes a dip portion.
25. A guide sleeve assembly for defining a protective passageway in
tissue of a patient, comprising: a tube defining an interior
working channel adapted to receive surgical instruments, wherein
said tube has at least one visualization window defined therein for
viewing the surgical instruments in said interior channel; a cover
disposed on said tube adjacent said window, said cover being
adapted to selectively cover said window to prevent tissue invasion
into said interior channel through said window; and wherein said
tube includes at one end a distractor and a lateral extension.
26. A guide sleeve assembly for defining a protective passageway to
a disc space in a patient, comprising: a guide sleeve, said guide
sleeve including a first tube defining a first working channel
adapted to receive surgical instruments, wherein said first tube
defines at least one first visualization window for viewing the
surgical instruments in said first working channel, and a second
tube laterally joined to said first tube, said second tube defining
a second working channel and at least one second visualization
window; and a cover slidingly disposed on said first tube adjacent
said first window, said cover being adapted to selectively cover
said first window to prevent tissue invasion into said first
working channel through said first window.
27. The guide sleeve assembly of claim 26, wherein said cover is
further slidingly disposed on said second tube adjacent said second
window to prevent tissue invasion into said second working channel
through said second window.
28. The guide sleeve assembly of claim 27, wherein said cover
includes a dip portion between said first and second tubes.
29. The guide sleeve assembly of claim 26, further comprising: a
second cover slidingly disposed on said second tube adjacent said
second window, said second cover being adapted to selectively cover
said second window to prevent tissue invasion into said second
working channel through said second window.
30. The guide sleeve assembly of claim 29, wherein said cover and
said second cover each has a partial cylindrical shape.
31. The guide sleeve assembly of claim 30, wherein said partial
cylindrical shape extends approximately 200.degree..
32. The guide sleeve assembly of claim 30, wherein said partial
cylinder shape extends approximately 270.degree..
33. The guide sleeve assembly of claim 29, wherein said cover and
said second cover each includes an outwardly extending flange
adapted for tissue retraction.
34. The guide sleeve assembly of claim 26, wherein: said guide
sleeve has a proximal portion and an opposite distal portion
adapted for insertion into the patient; said proximal portion has a
first outer width that spans said first and second tubes; said
distal portion has a second outer width that spans said first and
second tubes; and said second outer width is smaller than said
first outer width.
35. The guide sleeve assembly of claim 26, wherein said cover is
transparent.
36. The guide sleeve assembly of claim 26, wherein said cover has a
tapered leading edge to prevent tissue damage.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to surgical procedures for
spinal stabilization and more specifically to instrumentation
adapted for inserting a spinal implant within the intervertebral
disc space between adjacent vertebra. More particularly, while
aspects of the invention may have other applications, the present
invention is especially suited for disc space preparation and
inmplant insertion into a disc space form a generally anterior
approach to the spine.
Various surgical methods have been devised for the implantation of
fusion devices into the disc space. Both anterior and posterior
surgical approaches have been used for interbody fusions. In 1956,
Ralph Cloward developed a method and instrumentation for anterior
spinal interbody fusion of the cervical spine. Cloward surgically
removed the disc material and placed a tubular drill guide with a
large foot plate and prongs over an alignment rod and then embedded
the prongs into adjacent vertebrae. The drill guide served to
maintain the alignment of the vertebrae and facilitated the reaming
out of bone material adjacent the disc space. The reaming process
created a bore to accommodate a bone dowel implant. The drill guide
was thereafter removed following the reaming process to allow for
the passage of the bone dowel which had an outer diameter
significantly larger than the reamed bore and the inner diameter of
the drill guide. The removal of the drill guide left the dowel
insertion phase completely unprotected.
More recent techniques have advanced this concept and have provided
further protection for sensitive tissue during disc space
preparation and dowel insertion. Such techniques have been applied
to an anterior approach to the lumbar spine. In one approach, a
unilateral template has been provided to evaluate the space in the
disc space. For bilateral implant placement, the template entire
device must be rotated and visually aligned to approximately 180
from the previous position. Thus, there is the chance for operator
error in rotating the device to the correct position. Further,
there is little
More recent techniques have advanced this concept and have provided
further protection for sensitive tissue during disc space
preparation and dowel insertion. Such techniques have been applied
to an anterior approach to the lumbar spine. In one approach, a
unilateral template has been provided to evaluate the space in the
disc space. For bilateral implant placement, the template entire
device must be rotated and visually aligned to approximately 180
from the previous position. Thus, there is the chance for operator
error in rotating the device to the correct position. Further,
there is little guidance to ensure proper alignment of cutting
instruments extending through the template.
One approach to provide such alignment is the use of a guide wire
extending through a cannulated cutting instrument, such as a
trephine. However, for instruments with hollow cutting heads, there
is typically no engagement between the inner walls of the hollow
cutting head and the guide wire. Thus, the guide wire may bend
between the portion extending into the tissue and the guide wire
entrance into the cannula of the instrument. As a result, the
hollow cutting head may not remain in substantial alignment with
the guide wire, resulting in improper opening formation. Therefore,
there remains a need for improved guiding mechanisms for cutting
instruments.
Once an initial opening or openings have been made in the disc
space, the height of the disc space is normally distracted to
approximate the normal height. Typically, a first distract or with
a height estimated by CT or MRI examination is inserted. If
additional distraction is required, the first distractor is removed
and a second, larger distractor is inserted. However, since the
positioning of the distractors is usually performed without the
benefit of protective guide sleeves, the switching of distractors
increases the potential for damage to neurovascular structures and
may increase the time of the procedure.
For bilateral procedures, a double barrel sleeve may be inserted
over a pair of previously placed distractors with a central
extension extending into the disc space to maintain distraction.
One limitation on guide sleeve placement is the amount of
neurovascular retraction that must be achieved to place the guide
sleeves against the disc space. For some patients, a double barrel
sleeve may not be used because there is insufficient space to
accept the sleeve assembly. Further, although the distal end of the
sleeve assembly may be configured to engage the vertebral surface,
if material has been removed from the disc space, there is the
potential that adjacent neurovascular structures may encroach on
the working channels in the disc space, resulting in damage to
these structures caused by contact with instruments. While
visualization windows on the guide sleeve may assist in better
visualization of procedure steps and verifying unobstructed working
channels prior to tool insertion, the windows themselves may allow
tissue to come into contact with instruments in the working
channels. Thus, there remains a need for guide sleeves requiring
reduced neurovascular retraction for proper placement and providing
greater protection to adjacent tissue.
With guide sleeves in place, the disc space and end plates may be
prepared for receipt of an implant. Typically, cutting instruments
are advanced to remove disc material and bone. Such operations may
be time consuming since it is often necessary to adjust depth stop
equipment and to remove the instruments to remove cutting debris.
Since it is desirable to shorten the time of the operative
procedure, there remains a need for improved cutting instruments
and depth stop mechanisms.
While the above-described techniques are advances, improvement is
still needed in the instruments and methods. The present invention
is directed to this need and provides more effective methods and
instrumentation for achieving the same.
SUMMARY OF THE INVENTION
The present invention relates to methods and instrumentation for
vertebral interbody fusion. In one form, the method contemplates
gaining access to at least a portion of the spine, marking the
entrance point or points in the disc space, creating an initial
opening in the disc space through a template, distracting the disc
space and positioning an outer sleeve defining an interior working
channel adjacent the disc space. In a preferred embodiment, the
template can be inserted in a reduced sized configuration, with a
first portion engaging the tissue. The template may then be
manipulated to a larger configuration for bilateral insertion
procedures by movement of a second portion, without repositioning
the first portion. Additionally, a template according to the
present invention may include trephine guides that accommodate a
variety of different diameter trephine cutting heads. Specifically,
trephines according to the present invention may include an upper
shaft having a uniform diameter regardless of trephine cutting head
diameter. Thus, the upper guides of the template maintain the
trephine in axial alignment regardless of whether the lower guide
engages the trephine head. In another aspect of the invention, an
improved guide member is provided to maintain alignment of cutting
instruments.
Once an initial opening or openings have been defined in the disc
space, a distractor may be inserted to distract the disc space to
the desired height. Various distractors according to the present
invention may be used to distract the disc space. One such
distractor has a first position that provides a first working
distraction height in the disc space and a second position that
provides a greater second working distraction height. Should the
first working distraction height be insufficient, the distractor
according to the present invention may be rotated one quarter turn
to create a second greater distraction height in the disc space.
Additionally, in a further preferred aspect of the invention, a
modular distractor mechanism according to the present invention may
be configured to accept many different rotatable distractor tips
and may releasable engage the tips such that a distractor tip may
be left in the disc space while permitting withdrawal of the
distractor tool shaft. With such a configuration, a single
distractor tool shaft may be use with various tips, thereby
limiting the total number of complete distractor instruments
required. Additionally, distractor tips may be made of radiolucent
material that will not inhibit x-ray imaging of the disc space.
Such distractor tips may include radiographic markers to indicate
the ends and/or outer edges of the device and markers to indicate
the rotational alignment of the distractors in the disc space.
Once the desired distraction of the disc space has been achieved,
the handle of the distractor may be removed and an outer sleeve
positioned over the distractor. For a bilateral approach, one or
both of the distractors may be left in position and a double barrel
sleeve positioned over the distractors and advanced toward the disc
space. A further step that may be performed in a preferred
embodiment is to select a removable distal tip for the outer sleeve
that matches the height of disc space distraction and the diameter
of the implant. Thus, an outer sleeve may be used with
interchangeable distal tips to accomplish the insertion. Whether
single or double, the sleeve is advanced until the leading
distractor portion of the outer sleeve is adjacent the disc space.
If necessary, a driving cap may be positioned over the proximal end
of the outer sleeve. The outer sleeve is then driven into position,
preferably with a spike or series of spikes engaging vertebrae
adjacent the disc space.
Although various sleeves are known in the art, in a preferred
embodiment, outer sleeves according to the present invention have a
reduced width portion adjacent the distal end to limit the amount
of retraction of the surrounding vascular and neural structures
required for the procedure. In a preferred form, a double barrel
sleeve assembly includes a central distraction flange having a
first height and an opposing pair of lateral extensions having a
second height, less than the first height. The lateral extensions
provide protection from encroachment of tissue into the working
area in the disc space. A further aspect of a preferred embodiment
includes the provision of visualization windows along the outer
sleeve for visual access to the interior working channel while
instruments are in the working channel. Various combinations of
windows are disclosed to accomplish the desired visualization.
While visualization is desirable, having openings in the outer
sleeve may allow surrounding vessels and tissue to migrate into the
working channel of the outer sleeve. Tissue and vessels present in
the working channel may be damaged by insertion and removal of the
tools (often with cutting edges) or during use of those tools.
Thus, the present invention contemplates covers over the windows
that may be selectively opened for visualization and closed to
prevent tissue and vessel infiltration. Additionally, the covers or
the outer sleeve may be transparent to allow visualization through
the windows without removing the covers or directly through the
sleeve. In a similar manner, an image guidance system such as that
available under the tradename STEALTH may be used in conjunction
with the present system to monitor the advancement and positioning
of instruments and implants. Even without the use of an imaging
system, the present invention discloses the use of manually
adjustable depth stop that may be used to control the steps of
trephining, reaming, tapping, and dowel insertion. The term dowel
is used in a broad sense throughout the disclosure and is intended
to encompass dowels made of bone, metallic cages and other implants
used for interbody fusion regardless of shape or material of
construction.
One aspect of the present invention comprises an outer sleeve with
a visualization window disposed adjacent a distal end and a cover
removably covering the window. In one preferred embodiment, the
cover includes a flange adjacent the distal end to mobilize vessels
and other tissue away from the ends of the outer sleeve. In one
form, the cover is slidably disposed on the upper surface of the
tube or tubes to cover only the upper windows. In another form, the
cover is slidably positioned on the tube to cover the upper and
lower windows of the tube.
In yet another aspect, the outer sleeve has a double barrel
configuration. The bone engagement end of the outer sleeve includes
a first flange having a first height sufficient to maintain
distraction. Preferably, the bone engaging end also includes a pair
of opposing lateral extensions having a second height less than the
first height. The lateral extensions are intended to inhibit
lateral encroachment of tissue into the working area in the disc
space but are not limited to maintain distraction.
Another aspect of the present invention comprises an adjustable
stop mounted on a tool shaft. The stop is selectively engageable
with the tool shaft at a plurality of locations along the tool
shaft by axial movement of a collar to control the position of the
stop engaging portions. With the collar in a first position, the
engaging portions are disengaged from the tool space. With the
collar in a second position, the engaging portion is urged into
engagement with the shaft. The tool shaft is sized to be received
within an outer sleeve and the stop is sized to prevent passage
within the outer sleeve. Thus, the stop may be selectively coupled
to the tool shaft to control the extent of tool shaft that may be
received within the outer sleeve. Although not required, in one
embodiment the stop includes a viewing window and the tool shaft
includes markings, whereby the markings are calibrated to indicate
to the user the extent of tool shaft extending beyond a distal end
of the outer sleeve.
Still another aspect of the invention comprises a reamer with a
reaming head having a plurality of reaming apertures in
communication with an internal channel. The internal channel
extends within the reaming head and proximally along at least a
portion of the reamer shaft. The internal channel includes a
proximal segment extending nonparallel to the longitudinal axis of
the reamer shaft, whereby reaming debris may be transferred to the
exterior of the reaming shaft.
The present invention further contemplates a method for interbody
fusion comprising, positioning a template adjacent a fusion site,
forming at least one initial opening in the disc space, distracting
the disc space, placing a distal portion of an outer sleeve into
the disc space, the outer sleeve including at least one
visualization window and cover removable disposed over the windows
and visualizing the surgical site through the windows. Preferably,
the method also includes removing the cover to expose the window
prior to visualization. Further, the method may include the step of
enlarging the opening with cutting tools and may further include
attaching an adjustable depth stop to the tool shaft prior to
extension beyond the distal end of the outer sleeve.
Related objects and advantages of the present invention will be
apparent from the following brief description of the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1a is a perspective view of an expandable template according
to the present invention.
FIG. 1b is a side elevational view of the template of FIG. 1a.
FIG. 1c is front view of the template of FIG. 1a.
FIG. 1d is a top view of the template of FIG. 1a.
FIG. 1e is a bottom view of the template of FIG. 1a.
FIG. 1f is an enlarged perspective view of the engaging end of the
template of FIG. 1a.
FIG. 2a is a perspective view of the template of FIG. 1a in an
expanded condition.
FIG. 2b is a top view of the template of FIG. 2a.
FIG. 3a is a side view of another embodiment of an expandable
template according to the present invention with a trephine
disposed therein.
FIG. 3b is a top view of the expandable template of FIG. 3a showing
the locking mechanism.
FIG. 4a is a perspective view of a guide member and trephine
according to the present invention.
FIG. 4b is an enlarged perspective view of a portion of FIG.
4a.
FIG. 5a is a perspective view of a distractor according to the
present invention.
FIG. 5b is an enlarged front view of the tip of the distractor of
FIG. 5a.
FIG. 5c is an enlarged side view of the tip of the distractor of
FIG. 5a.
FIG. 6 is a perspective view of a guide sleeve assembly according
to another aspect of the present invention.
FIG. 7 is a front view of the guide sleeve assembly of FIG. 6.
FIG. 8 is a side view of the guide sleeve assembly of FIG. 6.
FIG. 9 is a partial cross-sectional side view of a guide sleeve
assembly with a removable tip.
FIG. 10 is a perspective view of a guide sleeve assembly with a
cover according to the present invention.
FIG. 11 is an end view of the guide sleeve assembly of FIG. 10.
FIG. 12 is a front view of one embodiment of a guide sleeve window
cover according to the present invention.
FIG. 13 is a front view of a guide sleeve assembly with the cover
of FIG. 12 mounted thereon.
FIG. 14 is a perspective view of an engaging end of a guide sleeve
assembly with another embodiment of a window cover according to the
present invention.
FIG. 15a is a side view of a window cover.
FIG. 15b is an end view of the window cover of FIG. 15a.
FIG. 16a is still a further embodiment of a window cover in
accordance with the present invention.
FIG. 16b is an end view of the window cover of FIG. 16a.
FIG. 17 is an anterior to posterior view of a guide sleeve assembly
with window covers according to FIG. 15 disposed thereon, the guide
sleeve assembly is positioned in relation to a pair of adjacent
vertebral bodies and blood vessels.
FIG. 18 is a partial cross-sectional top view of a guide sleeve
assembly with only one window cover positioned thereon, a portion
of the guide sleeve assembly extending into the disc space.
FIG. 19 is a side view of a hollow headed reamer in accordance with
another aspect of the present invention.
FIG. 20 is the reamer of FIG. 19 rotated 90 degrees about the shaft
longitudinal axis.
FIG. 21 is an enlarged partial cross-sectional view of the head of
the reamer of FIG. 19.
FIG. 22 is a side view of a clean out tool for use with the hollow
reamer head of FIG. 19.
FIG. 23 is a top view of the clean out tool of FIG. 22.
FIG. 24 is a side view of a tap in accordance with the present
invention.
FIG. 25 is a side view of a tap having a removable tap head in
accordance with another aspect of the present invention.
FIG. 26a is a side view of a reamer having a removable reamer head
in accordance with another aspect of the present invention.
FIG. 26b is a partial cross-sectional view of the connection
mechanism of FIG. 26a.
FIG. 27 is a perspective view of a depth stop according to the
present invention with the collar partially retracted to expose the
locking fingers.
FIG. 28 is a side view of the depth stop of FIG. 27.
FIG. 29 is a cross sectional view taken along line 29--29 of FIG.
28.
FIG. 30 is a front view of the depth stop of FIG. 27 with the
collar fully extended.
FIG. 31 is a side view of an alternative embodiment of a depth stop
in accordance with the present invention.
FIG. 32 is a partial side view illustrating the depth stop of FIG.
31 in engagement in with a tool shaft.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
For the purposes of promoting an understanding of the principles of
the invention, reference will now be made to the embodiments
illustrated in the drawings and specific language will be used to
describe the same. It will nevertheless be understood that no
limitation of the scope of the invention is thereby intended, such
alterations and further modifications in the illustrated device,
and such further applications of the principles of the invention as
illustrated therein being contemplated as would normally occur to
one skilled in the art to which the invention relates.
The present invention relates to methods and instrumentation for
performing vertebral interbody fusion. Specifically, although
aspects of the present invention may have other uses either alone
or in combinations, the instruments and methods disclosed herein
are particularly useful for anterior lumbar interbody fusion.
Provisional application 60/081,206 filed Apr. 9, 1998 is
incorporated herein by reference.
Referring now to FIGS. 1(a) through (f), there is shown an
intraoperative template 10 for use in interbody fusion.
Intraoperative template 10 includes a central anchoring pin 12 and
two supplemental anchoring pins 14 and 16. These pins are adapted
to be driven into vertebral bodies or other tissue adjacent a disc
space to anchor the intraoperative template 10 in the proper
location. Template 10 includes an outer shaft 18 interconnected
with handle 22 and an inner shaft 20 disposed within outer shaft
18. Inner shaft 20 extends to encompass pin 12. Outer shaft 18 is
rotatable with respect to inner shaft 20. Disposed adjacent the
distal end of template 10 are guide members 24 and 26 connected to
inner shaft 20 and outer shaft 18, respectively. Preferably, guide
members 24 and 26 are substantially circular plates having an
aperture therein. Guide members 24 and 26 define openings 28 and
30, respectively, adapted to receive a trephine tool therethrough.
Trephine guides 34 and 36 are positioned along outer shaft 18 and
have openings 40 and 42, respectively, in alignment along axis 31
and are sized to receive a trephine tool shaft. In an alternative
embodiment, it is contemplated that inner shaft 20 may be connected
to guide member 26 and outer shaft 18 may be connected to guide
member 24.
In a first reduced size configuration for unilateral templating and
guiding, shown in FIG. 1a, guide members 24 and 26 are axially
aligned along axis 31 with openings 28 and 30, respectively, in
similar alignment. In this reduced size configuration, the
expandable template may be inserted into the body through a
relatively small opening and the template may be used for
unilateral templating and guiding of a trephine. In this position,
a trephine may be guided through guides 34 and 36 and guide members
24 and 26 to engage the tissue below. Moreover, referring to FIG.
3a, a trephine according to the present invention may have a
uniform diameter along most of its shaft such that it is a close
fit within guides 34 and 36. The close fit in guides 34 and 36
maintains axial alignment, while permitting trephine shaft
rotation. Thus, a single template 10 may be used with a variety of
sizes of trephine head diameters, provided the shaft has a
substantially uniform diameter.
Referring now to FIG. 1a, handle 22 is connected to outer tube 18
and may be rotated in the direction of arrow 32 to a bilateral
templating and guiding position. This action rotates outer shaft 18
with respect to inner shaft 20. Guiding member 26, guide 34 and
guide 36 are connected to outer shaft 18 and therefore rotate when
handle 22 is moved. In contrast, first guide member 24 is
interconnected with inner shaft 20 and remains stationary upon
rotation of handle 22. As shown in FIG. 2a, handle 22 is rotated
approximately 180 degrees to align second template 26 approximately
180 degrees from first template 24 and thereby expand the template
to its bilateral trephining position. Thus, a trephine procedure
may be conducted along axis 33 through guides 34 and 36 and second
member 26 to cut an opening in the disc space. Axis 33 is spaced
from axis 31 by a distance "D" representing the distance of spacing
of the midpoints between implants to be inserted. FIGS. 2a and 2b
show the first and second templates rotated 180 degrees with
respect to one another. FIG. 2b shows a top view of a bilateral
templating and guiding configuration. In this expanded
configuration, the outer edges of guide members 24 and 26 define
the total area necessary for placement of implants and instruments
having a specific configuration and size. While in a preferred
embodiment, cylindrical implants having diameters of 16 mm, 18 mm
or 20 mm may be used, it is contemplated that other diameters may
be used and other shapes such as, but without limitation, squares
and rectangles.
Shown in dashed line in FIG. 2b is a groove 39 formed in guide
member 24 and projection 37 defined on guide member 26 and
extending into groove 39. It will be understood that the engagement
between groove 39 and projection 37 maintains alignment and limits
rotation to 180 degrees. Thus, template 10 may be moved between the
reduced size configuration and expanded configuration, but the
groove and projection engagement limit further movement and will
provide a positive indication of 180 rotation, thereby eliminating
the requirement for visual alignment with the first position.
Referring now to FIG. 3a, there is illustrated a further embodiment
of an expandable template according to the present invention.
Template 600 is substantially identical to template 10 previously
disclosed above, with the exception that template 600 includes a
locking mechanism 613. Expandable template 600 includes a handle
626 connected to outer shaft 622. As in the previous embodiment,
template 600 includes a first guide member connected to inner shaft
624 and a second guide member 606 connected to outer shaft 622.
First guide member 608 includes spike 612 and inner shaft 624
extends to form central spike 610. Outer shaft includes guides 602
and 604. As shown in FIG. 3a, a trephine 601 may be positioned
through guides 602 and 604, and through guide member 606. The
cutting head 605 includes cutting teeth 611, a series of index
markings 607 and a window 609 to visualize the contents in the
hollow interior. Preferably, trephine 601 includes a central
cannula 603 extending from the handle to the cutting head.
A locking mechanism 613 is disposed between the inner and outer
shafts to prevent rotation. Referring to FIG. 3b, locking arm 614
is pivotally attached to inner shaft 624 by pivot pin 620. The
locking arm may be pivoted to extend through slot 616 in the outer
shaft and slot 618 in the inner shaft. It will be understood that
with locking arm disposed in the slots the inner and outer shaft
will be prevented from rotation. In a first locked position, the
shafts are aligned as shown in FIG. 1a in the reduced size
configuration. In a second locked position, the shafts are aligned
as shown in FIG. 3a in the expanded bilateral templating
configuration. It will be understood that the expandable, rotatable
template of the present invention permits insertion of the device
through a smaller opening than would have been permitted with a
fixed relation double trephine opening template. Further, the
expandable template may be locked in either a unilateral or a
bilateral position. Locking engagement in the bilateral position
insures accurate bilateral placement with consistency that would
not be readily achievable with a unilateral template particularly
where the surgeon must reposition the device by visual alignment.
Subsequently, the device may be rotated to an expanded
configuration suitable for trephine guiding to form bilateral
openings without removing the instrument.
In use, access to an anterior portion of the spinal column is
achieved by known method. Blood vessels, particularly the aorta,
vena cava, and branches thereof are mobilized to provide space for
bilateral implant placement. With the template in the reduced size
configuration of FIG. 1a, the template is inserted into the body
and advanced until the pins are disposed adjacent a disc space. The
circumference of the template guide member is selected to the
circumference needed for bilateral placement of a pair of implants.
More specifically, the area of the guide members of FIG. 2b closely
approximate the area needed for placement of the double barrel
guide sleeve disclosed herein, see for example FIG. 11. Central pin
12 is disposed centrally between the intended location of the
implants. In either the unilateral or expanded bilateral condition,
the template may be disposed adjacent the disc space to measure the
space available for implant and instrument placement. If the space
appears too small, a smaller sized template may be inserted to
evaluate the space. In the bilateral condition, the template
approximates the area needed for implant and instrument placement.
Vessels disposed within the templated area may need to be mobilized
outside the area or an alternative implant size or approach may be
utilized. Further, osteophytes that appear within the templated
area may be removed to prepare for engagement with a guide sleeve.
Once the area is cleared, the pins are inserted into the tissue of
the disc space and/or adjacent vertebra to anchor the template,
thereby maintaining its position during subsequent steps. As shown
in FIG. 3a, a trephine is inserted into the guides and through the
guiding members. The trephine is cuttingly advanced into the disc
tissue to form an opening therein. The trephine may then be at
least partially removed from the template to permit movement
between the first and second guide members. If a lock mechanism is
used, the locking arm must be moved to an unlocked position and the
handle rotated to rotate the upper guide member to the expanded
bilateral templating position. The trephine is reinserted and
advanced through the upper guide member to form a second opening
aligned with and offset a distance D from the first opening. Thus,
the template permits controlled bilateral opening formation through
an expandable and collapsible template. The template may be
collapsed into its reduced size form and withdrawn after completion
of the trephining operation.
Referring now to FIGS. 4a and 4b, there is shown a further guiding
device according to the present invention. Guiding member 450
includes an elongated shaft 430 having a substantially uniform
diameter over most of its length. Shaft 430 includes a distal
portion adapted for guiding a cutting instrument having a hollow
cutting head. The distal portion of shaft 430 includes distal end
432 having a sharpened tip 434 adapted to penetrate tissue,
specifically tissue disposed in the disc space. Distal end 432
includes markings 444 which indicate the extent of shaft 430
disposed in the disc space. Although guide member is preferably
formed of stainless steel, other bio-compatible materials are
contemplated. Specifically, shaft 430 may be formed of a
radiolucent material and markings 444 may be radiopaque. Adjacent
distal end 432 is enlarged portion 436 having a diameter
substantially greater than the shaft diameter. Enlarged portion 436
is adapted to prevent further advancement of guiding member 450
into the tissue and to guide the cutting of the cutting tool.
Enlarged portion 436 preferably includes a planar surface 442
substantially perpendicular to the longitudinal axis of shaft 430.
A substantially spherical surface 440 is disposed adjacent planar
surface 442. This is followed by a tapering conical surface 438
that is adapted to align the cutting head over enlarged end 436. It
will be understood that the internal surface of cutting head 426
defining opening 428 engages the transition line 448 between
spherical surface 440 and taper surface 438. The diameter of
transition line 448 substantially matches the internal diameter of
cutting head 426 to provide a close fit for maintaining
alignment.
In use, guide member 450 is inserted into the body with distal end
432 fully inserted into the tissue of interest, preferably disc
tissue although other uses are contemplated. Cutting tool 420 is
advanced over guide member 450 with shaft 422 in substantial
alignment with shaft 430 extending through channel 427. While a
trephine is illustrated, other cutting tools such as, but without
limitation, reamers and non-rotary cutting tools may be used with
guide members according to the present invention. Cutting teeth 425
are positioned adjacent enlarged portion 436 and are advanced until
the cutting teeth surround the enlarged portion. It will be
understood that if cutting teeth are offset with respect to
enlarged portion 436, the teeth will engage a portion of conical
surface 438 and thereby be urged into alignment. Enlarged portion
436 is received within chamber 428 and cutting teeth 425 are
advanced along distal portion 432 until conical surface 428 abuts
internal conical surface 429 to prevent further advancement. The
assembly may be withdrawn with the cut tissue impaled by distal
portion 432. The tissue may be removed from chamber 428 by
advancing the guide member with respect. to the cutting head such
that the enlarged portion urges the tissue out of the hollow
interior. This may be particularly helpful where the cutting tool
is used to extract a bone graft. The depth of cutting teeth
penetration may be adjusted by placement of the enlarged portion.
Additionally, while only a single enlarged portion is shown, more
than one may be positioned on the shaft to further adjust the guide
member depth and cutting depth of the tool.
Referring now to FIGS. 5a-c, there is shown a disc space distracter
50 according to one aspect of the present invention. Distractor 50
includes a proximal end 53 configured as an enlarged end for
engagement with a conventional Hudson connection on a T-handle (not
shown). Shaft 54 is joined with a distracter tip 56. While an
integral shaft and head are shown, head 56 may be removably
attached to shaft 54. One such removable attachment is more fully
disclosed in provisional application 60/081,206 incorporated herein
by reference. Distracter tip 56 is designed such that it can be
inserted in a disc space to establish a first working distraction
height 72 (see FIG. 5b), which is less than a second working
distraction height 70 (see FIG. 5c). More specifically, distracter
tip 56 has a rounded leading edge 62 that extends to opposing
inclined surfaces 58 and 59 which extending more proximally blend
into substantially planar opposing surfaces 60 and 61,
respectively. Planar surfaces 60 and 61 extend in parallel
alignment along the longitudinal axis of the distracter to
establish height 72. It will be understood that the inclined
surfaces 58 and 59 cooperate to ease insertion into the disc space
and to initially distract the disc space to at least a height 72.
If first height 72 is sufficient, further procedures as known in
the art may then be carried out to accomplish implant insertion.
Alternatively, rounded leading edge 62 permits the distractor to be
inserted to directly achieve second distraction height 70.
In an alternative aspect, should first height 72 be insufficient,
head 56 may be rotated a quarter turn, or 90 degrees, to the
position shown in FIG. 5c. Rounded surfaces 64 and 66 engage the
bone to urge it apart and into a second larger distracted height
70. It will be understood that utilization of a distracter tip as
disclosed in the present invention, permits a two-height
distraction of the disc space that may be carried out with a single
instrument and without removing the instrument from the disc space.
This offers an advantage to the surgeon of a single instrument
offering multiple useful distraction heights. Thus, a surgeon may
initially believe a disc space will need a first amount of
distraction. After insertion of the distractor, the surgeon may
discover that further distraction is required. In this situation, a
distractor according to the present invention allows further
distraction without instrument withdrawal. Moreover, distractor
head 56 limits the number of instruments that must be made
available to surgeon to accomplish a surgical procedure by
providing two working distraction heights on a single tool.
Specifically, but without limitation, the distraction heads may be
formed with first heights 72 ranging from 6 mm to 12 mm and second
heights ranging from 7 mm to 13 mm. Preferably, heights 70 and 72
vary by 2 mm increments. More preferably, height 72 is 8 mm and
height 70 is 10 mm. In another form, height 72 is 10 mm and height
70 is 12 mm. Other variations may be utilized that provide multiple
working distraction heights that approximate the disc height in a
normal spine.
Referring now to FIG. 6, there is shown a double-barrel guide
sleeve assembly 100 having a first sleeve 140 connected to a second
sleeve 142. Sleeves 140 and 142 each define working channels 130
and 132 extending in a substantially unobstructed manner from the
proximal end 102 to distal end 104. Assembly 100 includes upper
windows 106 and 108 formed in sleeves 142 and 140, respectively,
that are adapted for engagement by a removal tool. The sleeves also
include lower elongated visualization windows 110 and 112.
Adjacent distal end 104, the material thickness along the outer
edge of each tube 140 and 142 is reduced in order to provide a
smaller cross-sectional area for the sleeve assembly as well as a
reduced width extending transverse to the longitudinal axis of
assembly. The reduced cross-sectional area and smaller width
reduces the amount of retraction of vessels adjacent the disc space
that would be required without the reduction. Side wall 114 is
shown as an indication of the reduced thickness of the device in
the distal area 104.
Distal end 104 includes a central distracting flange 116 which may
be inserted into the disc space to achieve or maintain a height H1
of distraction between two vertebral bodies. Lateral flanges 118
and 120 also extend partially into or adjacent to the disc space.
However, in a preferred embodiment, lateral flanges 118 and 120
have a height H2 that is less than height HI. Thus, they do not
provide distraction of the disc space but are provided primarily to
protect surrounding vessels and neurological structures from damage
during the procedures. Although that is the function of the lateral
flanges in the preferred embodiment, it is contemplated that they
could be sized to provide distraction within the disc space in
conjunction with central flange 116. Additionally, distal end.104
includes spikes 122, 124, 126, and a fourth spike which is not seen
in the view of FIG. 10. These spikes may be urged into the bone of
the adjacent vertebral bodies to hold the double-barrel guide
sleeve 100 in a fixed position relative to the vertebral bodies. It
will be understood that windows 110 and 112 provide the medical
staff with the opportunity to visualize the instruments as well as
the openings in the disc. space and vertebral bodies, without
entirely removing instrumentation from guide sleeve 100.
Referring more specifically to FIG. 7, double-barrel guide sleeve
100 is shown in a front view to further illustrate an additional
aspect of the invention. Opposite vertebrae engaging end 104, the
guide sleeve has a width WI approximately twice the diameter of one
of the sleeves. Adjacent vertebrae engaging end 104 of the sleeve,
each of the outer portions of the sleeves has a reduced wall
thickness at side walls 114 and 113. The walls are not entirely
flat but have a substantially greater radius of curvature (see FIG.
11) giving the appearance of substantially flat walls but providing
a reduction in wall thickness over a greater area and tapering to
the full wall thickness at the termination of side walls 113 and
114. The reduced wall thickness on the lateral portion of each tube
reduces the overall width of the device to a width W2. The
reduction in width decreases the amount of retraction that vessels
in the area must be moved. The desirable reduction in width is
accomplished with little reduction in the strength of the device
since much of the structural integrity, particularly resistance to
axial compression during insertion of the sleeves, is carried by
the much thicker central portion where the two sleeves are joined
to each other. Preferably, the central portion may have a thickness
equal to two tube wall thickness.
As a further alternative, FIG. 9 shows that guide sleeve assembly
190 may be provided with removable barrel tips 191 having different
distraction heights, lateral extensions, or spike patterns. Barrel
tips may also have different diameters corresponding to the
placement of implants with different diameters. Removable tips 191
may be held in place by any of a variety of known connection
mechanisms. However, in a preferred embodiment, guide sleeve
assembly 190 includes a pair of opposing flexible fingers 192 and
193 having projections 194 and 195, respectively. Projections 192
and 193 on the flexible fingers extend into grooves 196 and 197,
respectively, defined in the removable tip. To limit proximal
movement of tip 191 during insertion, tapered surface 198
abuttingly engages shoulder 199 and the central portion between the
upper guide tubes. Use of a removable tip according to the present
invention not only allows use of interchangeable tips to suit a
specific application, it also permits removal of the outer sleeve
after placement in the body. With only tip 101 in place, the
posterior aspect of the disc space or spinal canal may be more
easily visualized and accessed.
Referring now to FIGS. 10 and 11, there is shown a further
embodiment of a double-barrel guide sleeve similar in most respects
to outer sleeve 100 of FIG. 6. The further embodiment of FIG. 12
differs from that of FIG. 6 in that guide sleeve 100 included only
a single elongated visualization window for each sleeve. In
double-barrel guide sleeve 150, each sleeve has a total of four
windows, two on an upper surface and two on a lower surface. Thus.
as shown in FIG. 10, windows 152, 154, 156, 158 provide the surgeon
with the opportunity for visualization along the majority of each
working channel. The back side of guide sleeve 150 has a similar
configuration.
Guide sleeve 150 is used in a similar fashion to the outer sleeve
100. In a preferred embodiment, outer sleeve 100 is provided with a
cover 160 having a length 162 sufficient to cover all four windows
disposed on at least one side of the device. Cover 160 is provided
to prevent possible damage to tissues which may invade the working
channel through the windows and be damaged by the operation,
insertion or removal of tools in the working channels. It is
contemplated that cover 160 may be transparent to allow
visualization directly through the cover or that it could be
opaque, requiring that the cover be repositioned prior to
visualization. It is further contemplated that the cover may have a
length 162 sufficient to extend over all the windows on one side
and it may be able to selectively cover either proximal windows 156
and 158 or all of the windows. Leading edge 163 is tapered to
prevent damage to tissue, particularly when moving forward to cover
the windows. The taper should urge the tissue out and away from the
guide sleeve. Further, cover 160 includes a dip 171 substantially
following the contour between the pair of guide sleeves.
Although other attachment mechanisms are contemplated, as shown in
FIG. 11, cover 160 is held in place by retaining pin 170 connected
through cover 160 to a lower dovetail portion 172. Dovetail portion
172 is slidable along a dovetail groove defined by grooves 168 and
169 defined within the outer body of guide sleeve 150.
FIGS. 10 and 11 show one embodiment of a cover for slidably and
selectively covering a plurality of windows in outer sleeve 150.
FIGS. 12 through 16b illustrate yet further embodiments of a cover
which may be displaced to expose underlying windows in one of the
double-barrel tubes. Further, although the covers are disclosed for
use with double barrel assemblies, it is contemplated that they may
be used with single tube guide sleeves without undue modification.
In the further embodiments, the working channel and visualization
windows of one barrel may be exposed while a cover remains in place
on the alternate barrel.
Referring to FIG. 12, partially cylindrical cover 182 consists of
elongated portions 183 and 185 which are sized to cover underlying
visualization windows. The elongated portions are retained on the
guide sleeve by connectors 184 and 186 that are sized to extend
around the exterior of the outer tube and guiding portion 188. It
is contemplated that connectors 184 and 186 may engage a cover
portion on the oppostie side of the guide sleeve identical to that
shown in FIG. 12. While cover 182 is disclosed as having elongated
members 183 and 185 interconnected, it is contemplated that each of
the covers 183 and 185 could be separate to allow visualization of
the windows only on an upper or lower surface of the working tube
without opening the opposing window.
Referring to FIGS. 14 through 16b, there are shown still further
embodiments of window covers according to the present invention.
FIG. 14 shows a cover 510 that covers approximately 200.degree. of
a single sleeve 502 of a guide sleeve assembly 501 similar to that
of FIG. 6. The cover includes an internal passage 515 and is
slidable along sleeve 502. In a further aspect, cover 510 includes
an enlarged flange 512 adjacent bone engaging end 504. Tapered
surface 513 extends between flange 512 and the outer diameter of
cover 510. Referring to FIGS. 15a and 15b, cover 514 includes a
flange 516 that extends along the entire leading edge of the cover.
The cover extends in a partial cylinder lacking material over angle
517.
Angle 517 is approximately 160.degree., thus material extends
around approximately 200.degree. of the cylindrical shape. It will
be understood that covers 510, 514, and 520 may be configured to
have material extending less than 200.degree. around the cylinder
to allow rotation of the cover in relation to a guide sleeve such
that the cover may be rotated to uncover a window. Thus, for covers
510 and 514, the flanges may continue to hold the vessels away from
the guide sleeve even when moved to allow access through one of the
windows.
An alternative embodiment shown in FIGS. 16a and 16b does not
include the enlarged flange 512. Cover 520 has a uniform end 524
and defines an internal channel 522 adapted to receive a guide
sleeve. However, in certain surgical procedures it is desirable to
use the embodiment having the flange to protect closely adjacent
vessels and to urge them away from the distal end of the guide
sleeve where it might be possible to contact instruments disposed
therein. Without the use of a cover, the outer sleeves may not
match the shape of the surface of the vertebral body thereby
allowing the potential for contact between instruments in the outer
sleeves and closely adjacent vessels. This is particularly
dangerous when operating close to the vena cava and aorta. However,
as shown in FIGS. 17 and 18, the flanges on the covers act as a
retractor to urge the vessels away from the outer sleeves.
Referring more specifically to FIG. 17, guide assembly 550 is
illustrated as being inserted into a disc space D between two
adjacent vertebra V1 and V2. Disposed adjacent the guide assembly
550 are vessels 562 and 560 graphically representing portions of
the aorta or vena cava. Covers 556 and 558 are mounted on guide
tubes 552 and 554, respectively. Flanges on the covers, shown more
clearly in FIG. 15a, urge the vessels away from the guide tube and
more importantly, away from working channels 553 and 555 were tools
would be inserted. Vessels 560 and 562 are most closely adjacent
guide tubes 552 and 554 near V.sub.1. Thus, lateral extensions on
the guide assembly may be insufficient to prevent contact between
vessels and tools in all applications.
Referring now to FIG. 18, there is shown a top view of a guide
assembly 580 positioned in the disc space adjacent a vertebral body
591. The guide assembly 580 includes a central distractor 582 and
lateral extensions 584 and 586. Spikes 590 and 592 may be inserted
into the bone of the vertebral body. For the purposes of
illustration, cover 596 has been positioned over a first guide
tube, while guide tube 595 with window 593 remains uncovered. Bone
engaging end 594 does not entirely conform to vertebra surface 589,
thus allowing the possibility of vessel migration into the working
channels. Cover 596 with flange 598 urges vessel 599 away from the
engagement between bone engaging end 594 and bone surface 589. In
contrast, vessel 597 is positioned adjacent the interface between
the guide tube and bone, resulting in the potential for vessel
migration into the working channel via the space between the bone
engaging end 594 and bone surface 589. Thus, covers according to
the present invention may also be useful to further retract vessels
away from the interface between the bone engaging end of the guide
assembly and the bone surface.
Referring now to FIGS. 19 through 21, there is shown a reamer 200
according to the present invention. FIG. 20 shows the reamer 200 of
FIG. 19 rotated 90 degrees. Reamer 200 includes a cutting head 202
having cutting flutes 203 with troughs 205 disposed therebetween.
Disposed in trough 205 is an aperture 204 extending to interior
channel 209. A series of apertures 204 are defined in the cutting
troughs and communicate with interior channel 209. The interior of
cutting head 202 is hollow and forms interior channel 209. Interior
channel 209 has a first portion with side walls substantially
parallel to the longitudinal axis and a second portion defined by
side walls extending at an angle to the longitudinal axis.
Preferably the second portion extends at a non-orthogonal angle to
permit easy cleaning. The second portion is connected to aperture
208 formed on the outer surface of the shaft and spaced from the
cutting head. It will be understood that aperture 208 permits
material cut by reaming head 202 to move through the interior
channel 209 to exit at aperture 208. Moreover, the reduced diameter
segment 211 defines an area between the shaft and outer sleeve
where debris from the cutting operation may collect prior to
removal of the device. This collection area has a length 214 in a
preferred embodiment, although it is understood that this could be
extended to increase the volume of material that may be collected.
This configuration permits completion of the cutting operation
without a requirement to remove the reamer to clean the collected
debris. Additionally, the debris may be visualized through outer
sleeve windows for evaluation.
Reduced diameter shaft 211 extends proximally to tapered region 210
which expands to a larger diameter guiding portion 212. Tapered
region 210 assists ease of insertion and guiding of the shaft of
the reamer within an outer working sleeve as previously disclosed.
Larger diameter guiding portion 212 is sized to have a reasonably
close fit within an outer working sleeve to permit rotation of the
device, yet limit the amount of transverse movement within the tube
to insure accurate reaming within the bone. Reamer 200 may thereby
be guided by a guide sleeve. Shaft 216 interconnects the proximal
end to the enlarged area 212.
Disposed on shaft 216 are a series of numbers 218, which indicate
the depth the reamer extends into the bone beyond the edge of a
cooperable guide sleeve. As can be appreciated from examining FIGS.
19 and 20, the numbers are displayed in a stepped arrangement
around the circumference of shaft 216. This stepped arrangement
permits each number to be larger, in the preferred embodiment three
times larger. than they could be if all numbers were listed in a
single column along the device. Thus, this arrangement permits easy
visualization of the number by the surgeon despite the small
incremental adjustment of the device. preferably 1 mm increments.
Extending more proximally along the shaft 216 are a series of
grooves 221 which are adapted to engage a depth stop mechanism
(described further below) to adjust the reaming depth of the
device. On the proximal end 220 is a Hudson-type connection for
engagement with a T-handle or other type of handle.
Referring now to FIGS. 22 and 23, there is shown a clean out tool
700 adapted for use with the hollow reamer head described above.
Clean out tool 700 includes a head 702 having a diameter
substantially matching the diameter of internal chamber 209. Clean
out tool 700 includes a flexible portion 704. Flexible portion 704
is connected to shaft 708 which is connected to handle 706.
Flexible portion 704 allows the device to enter through opening 208
in the reamer and force material out open end 201 of the reamer
head as end 710 is advanced. This is an improvement over hollow
head reamers that do not provide a clean out channel.
Referring now to FIG. 24, there is shown a thread tap 230 for
tapping a reamed out bone space. Tap 230 includes a cutting head
232, and a reduced diameter shaft 233 adjacent head 232 for
providing space around the shaft between the outer tube for the
collection of debris from the tapping operation. A tapered surface
234 extends to an increased outer diameter area 236. As previously
explained with respect to reamer 200, tapered surface 232 permits
guiding of the tap within a guide sleeve and enlarged area 236 by
providing a reasonably close fit with the guide sleeve to maintain
the axial alignment of tap 230. Tap 230 includes incrementally
stepped depth markings 240 and a Hudson connection 242 as
previously disclosed with respect to reamer 200.
Referring now to FIGS. 25 through 26b, there are shown modular
cutting tools joined to a shaft. FIG. 25 shows a shaft 250
releasably coupled to tap head 252 by coupler 254. Similarly, shaft
250 is coupled to reamer head 256 by coupler 254. In FIG. 26a
reaming head 256 may be removed from shaft 250 at the connection
254. The reamer includes a reaming head 256 having only six cutting
apertures disposed around the head and a hollow internal chamber
connected to aperture 258. While any number of known connection
mechanisms may be used, FIG. 26b shows the use of an axially
displaceable collar 260 to release balls 262 and 263 from grooves
264 and 265 of the reamer head. Shaft 250 includes a hollow
extension 268 having apertures 270 and 271 to hold balls 263 and
262, respectively. Collar 260 includes a reduced diameter portion
276 adapted to urge balls 262 and 263 into grooves 264 and 265 to
lock the cutting head and shaft together. Collar 260 may be axially
displaced away from the cutting head to dispose an enlarged
internal diameter portion 278 adjacent the balls to allow them to
disengage grooves 264 and 265, thereby allowing the cutting head to
be disengaged from the shaft. The same mechanism may be used with a
variety of cutting heads.
Referring now to FIGS. 27 through 31, there is disclosed a depth
stop mechanism cooperable with the shaft of a tool and guide sleeve
such as previously disclosed. Such tools can include, without
limitation, a reamer, a tap, and an implant inserter. Depth stop
326 includes an enlarged circumferential abutment shoulder 330
adapted to engage the proximal end of an outer working sleeve to
prevent further advancement of the stop and any interconnected
shaft. Stop 326 further includes viewing windows 328 to permit
visualization of depth markings on a shaft extending within the
stop. Stop 326 includes a manually operated collar 332 which may be
axially displaced to allow flexing of fingers 334. Collar 332 is
normally urged into an extended position by spring 342.
Referring specifically to FIG. 29, fingers 334 include projections
336 extending internally and bearing surface 337 extending
externally. The internal projections 336 are configured for
engagement within grooves 221 (FIG. 20) defined along a tool shaft
of a working tool, and bearing surface 337 is configured to engage
collar 332. Additionally, each finger includes an external taper
portion 339 adapted for engagement with bearing surface 340 of
collar 332 to urge the fingers inwardly as the collar is advanced.
It will be understood that in a retracted position, bearing surface
340 of collar 332 will be substantially disengaged from taper 339
and permit fingers 334 to disengage from groove 221 of a working
shaft (FIG. 20). With collar 332 in the extended position shown in
FIG. 29, bearing surfaces 340 will bear against bearing surface 337
of each finger to urge projections 336 into grooves 221 of a tool
shaft. To release fingers, collar 332 may be moved in the direction
of arrow R until bearing surface 340 moves beyond tapered surface
339. The flexible fingers may then spring outward. In this manner,
a user may quickly and easily disengage the locking mechanism of
the stop to advance or retract a working tool and then re-engage
the stop at the desired position. Preferably, distal end 333 of
collar 332 will extend beyond fingers 334 to limit the possibility
that surgical staff may snag protective apparel on exposed
fingers.
In a first embodiment shown in FIG. 30, collar 332 is retained on
housing 334 by retaining pin 342 extending into the housing and
through a slot 344. Retaining pin 342 prevents rotation of collar
332 with respect to housing 334. In an alternate embodiment shown
in FIG. 31, collar 332 defines an L-shaped slot 346 which permits
axial displacement of collar 332 with respect to body 334, as well
as a slight amount of rotation within the slot. It will be
understood that the L-shaped slot 346 permits the depth stop
mechanism to be locked in at disengaged position which permits free
movement of the tool shaft through the depth stop. This is a
desirable construction in some instances for easy removal of the
depth stop from the tool shaft, as well as for utilization of the
tool without the constraints of a depth stop mechanism.
FIG. 32 shows a depth stop 326 engaged with a tool shaft having
grooves 360 and marking 362 to show the depth of the distal end of
the tool out of the guide sleeve 370. Abutment shoulder 330 is
sized to engage the guide sleeve to prevent further movement. It
will be understood that the depth of penetration may be adjusted
between a number of positions defined by engagement of the fingers
336 in grooves 360 of the tool shaft. The adjustment is easily
accomplished by axial movement of collar 332. Engagement with the
tool shaft is indexed by the spacing of grooves 360 on the tool
shaft so the exact location of the stop may be easily known. The
tool shaft may be rotated with respect to the stop mechanism to
display the appropriate depth numeral 362 in window 328.
While the invention has been illustrated and described in detail in
the drawings and foregoing description, the same is to considered
as illustrative and not restrictive in character, it being
understood that only the preferred embodiments have been shown and
described and that all changes and modifications that come within
the spirit of the invention are desired to be protected.
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